1. Technical Field
Electric drive system for an automotive vehicle.
2. Background Art
An electric drive system in an automotive vehicle typically includes a power electronics inverter and a permanent-magnet synchronous motor (PMSM). The inverter and the PMSM are typically spaced apart to reduce the total cost of the electric drive system and improve system package. Furthermore, the electric drive system may include an interlock system in an effort to increase the reliability and the safety of the electric drive system. The interlock system detects whether an electrical connection between the power electronics inverter and the PMSM is loose or disconnected. A three-wire high-voltage cable typically provides the electrical connection.
FIG. 1 illustrates a prior art three-phase PMSM electric drive system 1 of an automotive vehicle having an inverter 2, a motor 3, a three-wire high-voltage cable 4 connecting the inverter 2 and the motor 3, an interlock system 5, and three high-bandwidth current sensors 9.
The current sensors 9 of FIG. 1 sense currents flowing through the three-wire high-voltage cable 4 in the electric drive system 1 and generate three current signals. The three current signals indicate the amount of current flowing through the three-wire high-voltage cable 4. Due to the symmetry of the electric drive system 1, only two of the three current signals that the current sensors 9 produce are independent. Thus, the three current signals from the current sensors 9 can be summed to check the in-range error of the electric drive system 1. However, the current sensors 9 increase the cost, size, and need for non-standardized components in the electric drive system 1.
The interlock system 5 in the electric drive system 1 of FIG. 1 has a dedicated circuit 6 and a dedicated low-voltage signal cable 7. The dedicated low-voltage signal cable 7 is embedded into various parts of the electric drive system 1 and can form an electrical circuit with the dedicated circuit 6. The dedicated low-voltage signal cable 7 is embedded into the three-wire high-voltage cable 4 that connects the inverter 2 and the motor 3. In addition, the dedicated low-voltage signal cable 7 is embedded in connectors 8 of the three-wire high-voltage cable 4. Thus, the electric drive system 1 requires the use of non-standard components, such as the cable 4 and the connectors 8 that have the dedicated low-voltage signal cable 7 embedded therein.
The dedicated circuit 6 detects whether the dedicated low-voltage signal cable 7 completes an electrical circuit with the dedicated circuit 6. If the dedicated low-voltage signal cable 7 does not complete the electrical circuit, then the dedicated circuit 6 indicates that the three-wire high-voltage cable 4 does not properly electrically connect the inverter 2 to the motor 3. On the other hand, if the dedicated low-voltage signal cable 7 completes the electrical circuit, then it may be assumed that the three-wire high-voltage cable 4 properly connects the inverter 2 to the motor 3 since the dedicated low-voltage signal cable 7 completes the electrical circuit.
The interlock system 5 illustrated in FIG. 1 does not directly detect whether the three-wire high-voltage cable 4 properly connects the motor 3 and the inverter 2. Instead, the interlock system 5 merely indicates whether the dedicated low-voltage signal cable 7 completes an electrical circuit with the dedicated circuit 6. Completion of an electrical circuit with the dedicated circuit 6 does not conclusively indicate that the inverter 2 is properly connected to the motor 3. Consequently, the interlock system 5 illustrated in FIG. 1 may create false and unnecessary failure modes.
Furthermore, the interlock system 5 increases the cost of the electric drive system 1 because non-standardized components are used. The non-standardized components include the dedicated circuit 6, the three-wire high-voltage cable 4 having the dedicated low-voltage signal cable 7 embedded therein, and the connectors 8 including the dedicated low-voltage signal cable 7 embedded therein. Furthermore, the interlock system 5 uses the three high-bandwidth current sensors 9, which increases the cost of the interlock system 5.
It is often desirable or necessary to decrease the cost and size of the electric drive system in the automotive vehicle. Furthermore, it is often desirable or necessary to simplify or reduce the need for non-standardized components in the electric drive system. In addition, it may be desirable or necessary to increase the reliability of the electric drive system. Furthermore, it may be desirable or necessary to increase the efficiency, speed, and accuracy of the electric drive system.